Isolation and Characterization of Glycosphingolipids in Pig Adipose Tissue1

The glycolipids of pig adipose tissue were isolated and analyzed. A method for their extraction, purification, and subsequent characterization is described. The glycolipids were extracted with hot ethanol from the acetone-defatted tissue and separated into one neutral and five acidic glycolipid groups on a DEAE-Sephadex column. Each group was further fractionated by column chromatography using silicic acid and ‘Iatrobeads’ silicate. Eleven species of ganglio sides in addition to one neutral glycolipid were purified and partially characterized by TLC and GLC. Exact structures were established by direct mass spectrometry after permethylation of intact glycolipids and by GC-MS of the partially methylated carbohydrates after hydrolysis of the permethylated glycolipids. The pig adipose tissue was found to contain tetraglycosyl ceramide (globoside) and disialoganglioside (GDla) as the predominant glycolipids, and furthermore, small amounts of hematosides (N-acetyl and N-glycolyl), three species of fucose containing and two species of glucosamine-containing monosialogangliosides, GM1 ganglioside, another type of disialoganglioside (containing both N-acetyl- and N-glycolyl-neuraminic acid) and two species of trisialogangliosides were also found. One of the trisialogangliosides possessed a carbohydrate composition Glc/Gal/Gal/NAc/NeuNAc=1 :1: 1: 3 and appears to be a novel trisialoganglioside, GT2. The glycolipid content was about 12 μmol/kg of the original tissue and more than a third of it corresponded to disialoganglioside (GD1a). The adipose glycolipids had similar fatty acid compositions, in which docosanoic (22 : 0) and tetracosanoic (24 : 0) acids were predominant.